HP System Dictionary/XL General Reference Manual Vol 1 (32256-90004)

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departments of a company both want to use an entity called P-NUM. The Personnel department deﬁnes P-

NUM as a personnel number, while the manufacturing department wants to use it for part number.

System Dictionary easily handles this conﬂict by allowing you to create a domain for each application.

Within a single domain, System Dictionary does not allow two occurrences of the same type to have the

same name. For example, you cannot have two entities called PRODUCT-NAME of the same entity type

(for example ELEMENT) in the same domain. The same is true for relationships of the same relationship

type. However, System Dictionary does allow two entities that use the same name if the entities are of

different entity-types in the same domain. For example PRODUCT-NAME of type RECORD, and

PRODUCT-NAME of type ELEMENT do not conﬂict with each other. This also applies to relationships.

Using Domains as Partitions

Just as you can use an account in the MPE ﬁle system to contain a set of related ﬁles, you can use a domain

to contain a set of occurrences a speciﬁc application uses. For example, you may want to have similar sets

of occurrences for the Marketing, Personnel, Manufacturing, and R&D departments. You can easily

accomplish this by creating a domain for each of them, as shown in ﬁgure 4-1. Note that this also keeps

the occurrences for that application separate from those of all others in the dictionary.

The Common Domain

System Dictionary includes a built-in domain called the common domain, which is created when the

dictionary is initialized. You can use this domain as the standard dictionary, that is, the space where all

the standard entities and relationships reside, and it is accessible by any dictionary user.

The common domain in each dictionary may be its only domain, or instead, serve as the domain containing

information common to any number of local domains. (See the discussion on "linking", further on in this

chapter.) If you have no need for partitioning the dictionary, you would use the common domain only. You

can ignore the concept of domains, and when opening a dictionary, allow System Dictionary to default to

the common domain.

Local Domains

You can create your own domains, called local domains, which you can use as partitions or name spaces, as

described above. Local domains can be completely self-contained, that is, the occurrences contained in

them can have their own attribute values. Instead of the occurrences in each domain having their own

unique set of attribute values, which takes up more space and can make a dictionary "non-standard",

System Dictionary allows occurrences in local domains to share attribute values with occurrences in the

common domain. This saves space and creates a more standard dictionary, which is also easier to

maintain. Sharing attribute values is discussed further on in this chapter.

Creating Domains

You can create domains through either the System Dictionary intrinsics or an SDMAIN command. No

matter what method you use, an empty domain is created and given a user-speciﬁed name.

Domains and the Dictionary Structure

Although you can use the domain feature of System Dictionary to create separate sets of entities and

relationships, you cannot use it to create separate dictionary structure deﬁnitions. All domains in a

dictionary exist in the same dictionary structure, and therefore, regarding the structure, entities and

relationships are always speciﬁed and used the same way, no matter which domain you are using.

Accessing Domains